Salt tolerance of maize (Zea mays L.): the role of sodium exclusion

ABSTRACT The influence of NaCl and Na2SO4 on growth of two maize cultivars (Zea mays cv. Pioneer 3906 and cv. Across 8023) differing in Na+ uptake was investigated in two green‐house experiments. Na+ treatment with different accompanying anions (Cl−/SO42−) showed that ion toxicity was caused by Na+. While shoot growth of the two cultivars was markedly affected by salt in comparison to the control during the first 2–3 weeks, there were only slight differences between the cultivars. The shoot Ca2+ concentration was reduced in both cultivars, and the youngest leaves contained an even lower concentration compared with the rest of the shoot. During this first phase, Across 8023 tended to have higher concentrations of Ca2+ than Pioneer 3906. The Na+‐excluding cultivar Pioneer 3906 showed continuous, although reduced, growth compared with the control, while the Na+ concentration in the shoot decreased until flowering. Cultivar Across 8023 accumulated Na+ until flowering: the reduction in the growth of stressed plants was greater than that for Pioneer 3906. Leaves of cultivar Across 8023 showed clear toxic symptoms, while those of the more salt‐tolerant cultivar Pioneer 3906 did not. It is concluded that Na+ exclusion contributes to the salt tolerance of maize.